Table 1.

Study characteristics of the included studies.

Study	Design	Location	Drug Type	Inclusion Criteria	Experimental Group	Control Group	Age (Years)	Sex (M/F)	Outcome	Follow-Up
B Schmid 2001 [34]	RCT	Germany	Oral	Osteoarthritis of the hip or the knee	Willow bark extract two tablets twice daily for two weeks (corresponding to a dose of 240 mg salicin/day), 39 participants	Placebo two tablets twice daily for two weeks, 39 participants	Willow bark group: 52.4 ± 7.0, placebo group: 53.5 ± 10.5	59/19	Lequesne index, WOMAC-VA 3.0, diary VAS	14 days
C Biegert 2004 [37]	RCT	Germany	Oral	Osteoarthritis of the hip or knee	Willow bark extract two tablets twice daily for six weeks (corresponding to a dose of 240 mg salicin/day), 43 participants	Placebo two tablets twice daily for six weeks, 41 participants	Willow bark 62.9 ± 7.2, diclofenac 61.2 ± 6.6, placebo 62.4 ± 8.9	43/41	WOMAC-VA 3.0, overall efficacy, quality of life assessment (SF-36), tolerability (100 mm VAS)	6 weeks
C Biegert 2004′ [37]	RCT	Germany	Oral	Rheumatoid arthritis	Willow bark extract two tablets twice daily for six weeks (corresponding to a dose of 240 mg salicin/day), 13 participants	Placebo two tablets twice daily for six weeks, 13 participants	Willow bark 56.5 ± 8.9, placebo 60.1 ± 11.0	4/22	Pain score (VAS), number of tender/painful and swollen joints, physical function (HAQ disability index), severity of morning stiffness, overall efficacy, quality of life (SF-36 index), ESR, CRP in plasma concentration, numbers of patient had ACR criteria for improvement	6 weeks
DC Nieman 2013 [35]	RCT	United States	Oral	Joint pain in the knees, hip, ankles, shoulders, or hands	Instaflex™ Joint Support three capsules per day for eight weeks, 49 participants	Placebo (magnesium stearate), three capsules per day, 51 participants	Instaflex group: 57.6 ± 0.9, placebo group: 58.3 ± 0.8	17/83	WOMAC, health-related quality of life (SF-36), symptom logs, joint pain (12-VS), 6 min walk test, blood measure (CRP, IL-1, TNFα, IL-8, IL-10)	8 weeks